Method of decorating a glazed article utilizing a beam of corpuscular energy

ABSTRACT

The surface of an article, such as a glass envelope for an electric lamp, is provided with a decorative pattern or indicia by coating the article with a vitreous material that includes a substance (such as lead oxide) that undergoes a permanent change in color when heated under reducing conditions, subjecting the article to a laser beam and a reducing gas flame, and varying the position of the article relative to the beam at a speed and in a manner such that the beam scans the article and thereby melts preselected portions of the vitreous coating and changes the color of such portions. In the case of a vitreous or ceramic article that is susceptible to thermally-induced fracturing, the vitreous coating material is preferably deposited on the article in the form of a frit and the article is preheated to a temperature which is near or above its strain point, thus fusing the frit in place just before the glazed heated article is exposed to the reducing environment and laser beam. An apparatus and method for concurrently firing a glass frit on an article and color-etching the resulting glazed article with a laser having control means which includes a prototype article are also disclosed.

(is-1on2 val-0v LJOClEU l aLClll Petro et [54] METHOD OF DECORATING AGLAZED ARTICLE UTILIZING A BEAM OF CORPUSCULAR ENERGY [72] Inventors:James Petro, Little Falls; Clair M. Rively, Old Bridge, both of NY.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

[22] Filed: Mar. 30, 1971 [21] App1.No.: 129,438

[52] U.S. C1 ..2l9/l21LM,219/121 EM, 101/35,

[51] Int. Cl ..B23k 9/00 [58] Field ofSearch ..2I9/l21 L; 117/46 FC, 46PB, 117/175; 346/76 L; 264/80 [56] References Cited UNITED STATESPATENTS 3,465,352 9/1969 Carlson et a1. ..346/76 L 3,238,053 3/1966Morgan ..117/17 5 3,474,457 10/1969 Becker 346/76 L 2,372,761 4/1945Boyd 117/46 FC 3,482,008 12/1969 Hibshman. ..264/80 3,056,881 10/1962Schwarz ....2l9/5O 3,573,847 4/1971 Sacerdoti ..346/76 51 3,663,793 [4 1May 16,1972

Primary Examiner.l. V. Truhe Assistant Examiner-Gale R. PetersonAttorney-A. T. Stratton, W. D. Palmer and D. S. Buleza 57] ABSTRACT Thesurface of an article, such as a glass envelope for an electric lamp, isprovided with a decorative pattern or indicia by coating the articlewith a vitreous material that includes a substance (such as lead oxide)that undergoes a permanent change in color when heated under reducingconditions, subjecting the article to a laser beam and a reducing gasflame, and varying the position of the article relative to the beam at aspeed and in a manner such that the beam scans the article and therebymelts preselected portions of the vitreous coating and changes the colorof such portions. in the case of a vitreous or ceramic article that issusceptible to thermally-induced fracturing, the vitreous coatingmaterial is preferably deposited on the article in the form of a fritand the article is preheated to a temperature which is near or above itsstrain point, thus fusing the frit in place just before the glazedheated article is exposed to the reducing environment and laser beam.

8 Claims, 6 Drawing Figures SWITCHING MEANS Patented May 16, 1972 ,2Sheets-Shout 1 WITNESSES INVENTORS James Petro 0nd Clair M. Rlvely 2Sheets-Sheet Patented May 16, 1972 CROSS-REFERENCE TO RELATEDAPPLICATION The subject matter of this application is an improvementupon the invention disclosed in pending application Ser. No. 779,995filed Nov. 29, 1968 by the same inventors and assigned to the sameassignee as the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to the art of decorating articles and has particularreference to a novel method for forming an indicia or pattern on thesurface of an article, such as a glass lamp envelope, that is providedwith a vitreous glaze and thereby producing an article that has thedesired indicia or pattern permanently inscribed in its glazed surface.

2. Description of the Prior Art Various methods have been developed downthrough the years for decorating articles that are provided with acolored vitreous coatingvln the case of glass bulbs for incandescentlamps or other light sources, the desired decorative design or patterniscustomarily formed by masking certain areas of the bulb or removingselected portions of the coating with chemicals or'other suitable means.Both methods are tedious, costly and must be very carefully controlledif aesthetically pleasing results are to be obtained. This isparticularly true when the article is coated with a pigmented glass fritthat is fired and fused in situ to form a vitreous enamel or glaze.

SUMMARY OF THE INVENTION Briefly, the present invention provides a noveland efficient method for decorating the surface of a glazed article byutilizing a beam of corpuscular energy and either an oxidizing or areducing environment to modify the color of selected portions of theglazed surface.

According to one embodiment, the article is coated with a pigmentedglaze that contains a constituent, such as lead oxide, which istransformed into another substance and changes color when heated underreducing conditions, and the glazed article is then scanned by a laserbeam (or an electron beam) while exposed to a reducing gas flame toeffect the color change and produce the desired decorative pattern. Ifthe arti- 'cIe is made of glass or a ceramic material which willfracture when struck by the beam, the article is preheated to reducethermally-induced stresses in the article and thus prevent it fromcracking. In such cases, the article is coated with a suitable pigmentedglass frit and preheated with a gas flame which is initially oxidizingin nature thus firing the frit and heating the article above its strainpoint in a single operation. The resulting glazed heated article is thenconcurrently exposed to the laser beam and a reducing gas flame toeffect the desired color-etching.

Since laser and electron beams can be readily focused and preciselycontrolled, intricate decorative patterns and indicia can becolor-etched into the glazed surfaces of various articles at a rate andwith a consistency heretofore unattainable.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the inventionwill be obtained by referring to the accompanying drawing, wherein:

FIG. 1 is an elevational view of an apparatus for glazing andcolor-etching a lamp bulb in accordance with the present invention bymeans of a laser that is controlled by a photocell which scans aprototype bulb having the desired indicia painted thereon;

FIG. 2 is an enlarged cross-sectional view through a coloretched portionof the bulb, taken along line 11-" of FIG. 1;

FIGS. 3 and 4 are elevational and enlarged fragmentary views,respectively, of another glazed lamp bulb having a differentdecorativepattem color-etched into its surface in accordance with theinvention; and,

FIGS. 5 and 6 are similar views of decorated lamp bulb.

PREFERRED EMBODIMENTS OF THE INVENTION (FIGS. 1-2) Broadly considered,the present invention encompasses the concept of decorating the surfaceof a glazed article by scanning the article with a beam of corpuscularenergy, such as a laser beam, at a speed and in a manner such that thebeam melts preselected portions of the glaze or vitreous coating and, inconjunction with either an oxidizing or a reducing gas flame, changesthe color of such portions and thereby forms the desired pattern orindicia without affecting the other portions of the coating. Theinvention accordingly requires a glaze or vitreous coating whichcontains a constituent that changesfinto a material of a different hueor color when heated to a high temperature under reducing or oxidizingconditions. In FIG. 1 there is shown an apparatus for concurrentlyfiring a pigmented glass-frit coating 11 onto the surface of a glasslamp envelope 10, heating the envelope to a temperature above its strainpoint, and color etching the resulting glazed envelope with a laser beam14 in accordance with a preferred embodiment of the invention.

The apparatus is depicted in the process of color-etching a W" in thesurface of a'latem-shaped envelope 10 that is composed of conventionalsoda-lime glass and is coated with a layer 11 of a suitable pigmentedglass frit that contains lead oxide. As indicated by the arrows, theenvelope 10 is rotated about and advanced along its longitudinal axiswhile it is concurrently subjected to a gas flame from a burner 13 and alaser beam 14 that is generated by a stationary laser 16 which is sooriented that the laser beam is substantially normal to the coatedsurface of the envelope. The laser 16 comprises a watt CO type laser ofconventional construction that produces a beam of coherent radiationthat has a wavelength of 10.6 microns. Such lasers are well known in theart.

In this particular embodiment the pigmented glass-frit layer 11comprises a material that fonns a light-transmitting white glaze orenamelwhen fired under oxidizing conditions and is deposited ontheenvelope 10 in the form of a wet slurry or slip which dries to a powderytexture. The slip had the following formulation; 61.04 kilograms of ahigh lead, cadmium glass frit (marketed by the Ferro Corporation,Cleveland, Ohio as Lead Base Glass Frit VG 540) 3 kilograms of powderedTiO 1.45 kilograms of powdered ZrO 28.34 kilograms of isopropyl alcohol,and 300 cc. watter.

The aforesaid constituents were placed into a 15 gallon ball mill,milled for 24 hours and the resulting slip was sprayed onto theenvelopes and air dried. The resulting powdery layer fused into a smoothwhite enamel coating or glaze 11 when fired at a temperature of 700 C,by the burner 13. Since this temperature is very close to the softeningpoint (695 C.) and above the strain point (470 C.) of the soda-limeglass envelope 10, the white glaze comprised a tenacious and durablecoating and the heated envelope did not fracture when struck by thelaser beam 14. The fuel for the burner 13 consisted of a mixture ofnatural gas (or propane) and air (or oxygen, which mixture was initiallyadjusted to provide a flame that was oxidizing in character during thefrit firing operation. The fuel mixture to the burner 13 was thenadjusted to provide a flame which was reducing in character so that thelead oxide in selected portions of the glaze 11 was converted into leadwhen the glaze was subsequently struck and melted by the beam 14.

As will be noted, the laser beam 14 is focused onto the glazed surface11 of the envelope 10 by a lens 15 that is positioned between theenvelope 10 and laser 16 at a distance f from the envelope surface whichis equal to the focal length of the lens. A prototype envelope 18 of thesame size and shape as the envelope 11 being processed is rotated andaxially advanced at the same speed by an envelope-feeding mechanismwhich will be described.

still another type of The prototype envelope 18 has the desired indicia19, such as a W in the case here illustrated, outlined on its surface inblack print or other suitable contrasting material so that it will besensed or detected by a stationary photocell 20 that is supportedadjacent and abreast of the prototype envelope 18. The photocell 20 isso oriented that it scans the indicia 19 as the prototype envelope 18 isrotated and progressively advanced along its longitudinal axis. Theoutput of the photocell 20 is fed by conductors 22 into a suitableswitching means 24 which is, in turn, connected to the laser 16 byconductors 26 and controls the input to the laser so that the latter ispulse operated accordance with the electrical signals generated by thephotocell 20 as it scans the prototype envelope 18. The indicia 19 onthe prototype envelope 18 is thus reproduced in the glazed surface 11 ofthe envelope in the form of a series of dark lines 17 that are producedby the heating effect of the impinging pulses of the laser beam 14 anddefine a W which is denoted by the reference numeral 12.

As shown more clearly in FIG. 2, the lines 17 are raised slightly andseparated by portions of the glaze 11 that were not struck by the laserbeam 14 and thus retained their original white color. Due to thereducing nature of the flame from the burner during laser impingement,the lead oxide in the portions of the glaze 11 struck by the laser beam14 is converted into lead when the glaze is locally heated and melted bythe beam. The lines 17 thus have a silvery or black color, dependingupon the amount of reduction which occurs. The color density of thelines 17 and the indicia they delineate can accordingly be readilyvaried simply by adjusting the gas-air (or gas-oxygen) mixture fed tothe burner 13. In any event, the lines 17 define a pattern or indicia 12which is dark and sharply contrasts with the white glazed portions 11 ofthe envelope 10 not struck by the laser beam 14.

The width of the lines 17 or colored regions formed in the glazedsurface 11 can be increased by using a lens which slightly defocuses thelaser beam 14 and thus produces localized heating over a larger area orspot. Of course, the power input per unit area of the defocused beammust be sufficient to heat the glaze 11 to a temperature which willreduce the lead oxide to lead. Hence, a 100 watt laser will providelines 17 or etched areas of a given maximum dimension. If lines or areasof larger size are desired, then a more powerful laser must be used -orthe speed at which the beam scans the glazed surface must be reduced toone which enables the defocused beam to achieve the required heating andtemperature.

If any undesirable darkening of the white portions of the glaze 11occurs during the decorating operation, this can be corrected bysubjecting the color-etched envelope 10 to an oxidizing flame andre-oxidizing the lead in the aforesaid portions of the glaze. Suchsubsequent oxidizing-flame treatment will not materially change thecolor of the dark lines 17 due to the severity of the reduction of leadoxide into lead and the depth of coloration produced by the laser beam14.

As will be noted in FIG. 1, the envelope-feeding mechanism comprises aplatform 28 having an aperture 29 which accommodates an upstandingthreaded rod or spindle 30. The spindle 30 threadably engages a nut 32that is rigidly fastened to the underside of the platform 28 so that thelatter rises and falls as the spindle is rotated relative to the nut. Asuitable bulb-holder such as an annular chuck 34 is frictionally coupledto the spindle 30 by a spring-plunger assembly 35 that extends laterallythrough the chuck and is in pressured but slidable contact with thespindle. The chuck 34 is rotatably sup ported on the platform 28 by abearing 36 that is fastened to the upper surface of the platform. Thechuck 34 thus rotates along with the spindle 30 and concurrently is ableto move upwardly along with the platform 28 as it is advanced by theinteraction of the nut 32 and spindle 30.

The prototype envelope 18 is concurrently rotated in the same directionby a second spindle 31 that extends through a second opening (not shown)in the platform 28 and is frictionally coupled to a second chuck 37 thatis also rotatably mounted on the platform by a second bearing 28. Thespindles 30, 31 are rotated at a suitable speed by a conventionaldriving means 33 consisting of an electric motor and interconnectinggears or belts (not shown). The envelope 10 being processed and theprototype envelope 18 are accordingly, rotated at the same rate of speedand, since they are both carried by the platform 28, they are alsoadvanced upwardly relative to the laser beam 14 at the same rate ofspeed. Thus, an exact reproduction of the indicia 19 provided on thephoto-type envelope 18 is color-etched into the glazed surface 11 of theenvelope 10 by the laser beam 14. I

Since the profile of the envelope 10 is curved along the direction inwhich the envelope is being advanced relative to the laser beam 14,suitable means must be provided to maintain the laser beam in focusedrelationship with the glazed surface of the envelope 10 during thecolor-etching process. This is achieved in the apparatus shown in FIG. 1by mounting the lens 15 on a support 40 that is secured to a carrier 41which is reciprocally movable along a channel 42 provided in thestationary bed plate 43 of the apparatus. The channel 42 extendsparallel to the laser beam 14 and the carrier 41 is retained within thechannel by a spring 44 that is secured to holders 45, 47 attached to thecarrier and bed plate, respectively. The spring 44 urges the carrier 41toward a cam 48 that is fastened to and depends downwardly from theplatform 28 and presses a roller 46 located on the end of the carrier 41against the surface 50 of the cam 48.

As shown, the cam surface 50 has the same profile as the envelope 10.Thus, as the cam 48 moves upwardly along with the platform 28, thecarrier 41 is moved laterally by the action of the roller 46 and camsurface 50 in a manner such that the position of the lens 15 isautomatically adjusted to compensate for the difference in the spacingbetween the laser 16 and the glazed surface of the envelope 10 thatoccur as the envelope is advanced. The lens 15 is accordingly maintainedat a fixed distance f from the envelopes glazed surface 11 and the laserbeam 14 remains in focused relationship with the latter as itcolor-etches the indicia 12.

While no support means have been shown for the laser 16, drive means 33,bed plate 43, photocell 20, switching circuit 24 or burner 13, it willbe appreciated that all of these components are mounted on a suitableframe so as to constitute a unitary machine which operates in the mannerdescribed.

ALTERNATIVE EMBODIMENTS (FIGS. 3-6) The invention is not limited toproviding an isolated coloretched indicia or decorative pattern in theglazed surface of a glass lamp bulb but can be used to decorate anydesired area of the bulb. For example, as shown in FIG. 3, a continuoushelical silvery-black band 52 can be formed in a white leadoxidecontaining glazed surface 53 of a lamp envelope 54 by operating thelaser 16 continuously and concurrently rotating and axially advancingthe envelope 54 at a uniform rate relative to the laser beam 14 (as bythe apparatus shown in FIG. 1) so as to progressively color-etch theglaze 53.

As will be noted in FIG. 4, the darkened band 52 in the glaze 53 israised slightly but remains an integral part of the glaze. While some ofthe glaze is vaporized and removed by the action of the impinging laserbeam 14, the surface of the envelope 54 remains completely covered bythe glaze as shown.

Alternatively, a series of decorative patterns, such as randomly-spacedsnowflake" designs 55, can be color-etched in the white lead-oxidecontaining glazed surface 56 of a glass lamp envelope 57 as shown inFIG. 5. The "snow-flake dlesigns 55 are silvery-black against a whitetranslucent background and can be readily formed by properly programmingthe laser 16 and movement of the envelope 57 by means well known in theart.

As illustrated in FIG. 6, the designs 55 are again slightly raised fromthe envelope surface but constitute integral parts of the glazed coating56 as in the previously described embodiments.

OTHER EMBODIMENTS The invention is not limited to decorating soda-limeglass envelopes for lamps but may be used to color-etch various articlessuch as glazed metal or plastic vessels or bodies and lamp envelopes,mantles, etc. that are composed of high-silica content glass, quartz,polycrystalline alumina and other known semicrystalline or glass-ceramictype materials.

If the article is composed of material such as glass or polycrystallinealumina that has a high thermal expansion coefficient (that is, inexcess of approximately 15 X l per C), then the article should bepreheated to a temperature near or above its strain point ifthermally-induced stresses and resultant fracturing of the materialduring the color-etching of the glazed surface are to be avoided. Thisprecaution is not necessary in the case of quartz and similar materialswhich have coefficients of ex-pansion lower than approximately 15 X l0per C since they will withstand the thermal shock of the impinging laserbeam without fracturing. Quartz and fused silica have a coefficient ofexpansion of about 6 X 10" per C.

High content silica glass (over 96 percent silica) has an expansioncoefficient of about 8 X 10 per C and, thus, could also be color-etchedby a laser without preheating.

In the case of glazed metal or plastic articles, the only requirement isthat the glaze or vitreous coating contain a material that will beconverted into another material (or form) having a distinctivelydifferent color when the coating is heated by the laser or electron beamunder reducing or oxidizing conditions, or in a reducing or oxidizingatmosphere. As a specific example, a metal body that is coated with agreencolored fritted glaze which contains chromium oxide (or otherchromium compounds such as potassium dichromate) can be color-etched inaccordance with the invention to provide an indicia or pattern that isdefined by black lines or regions against a green-colored background.

By adjusting the power density per unit area of the impinging beam 14,portions of the glaze 11 on the bulb 10 can also be removed by the beamto provide a combination of sculptured transparent regions andcolor-etched glazed regions in the surface of the bulb.

We claim as our invention;

1. The method of decorating an article, which method comprises;

coating the article with a material that contains a constituent whichundergoes a color change when heated in a predetermined environment,

subjecting the coated surface of said article to a beam of corpuscularenergy and concurrently providing said predetermined environment thereatso that the portion of the coated surface which is struck by said beamis heated to a temperature sufficient to change the color of saidconstituent and the associated portion of said coating, and varying therelative position of said coated article and beam at a speed and in amanner such that the beam scans the coated surface of the article andchanges the color of selected portions of the coating and therebyproduces the desired indicia or pattern in the coated surface of thearticle. 2. The method of claim 1 wherein said predetermined environmentis one which is reactive in nature.

3. The method of claim 2 wherein said predetermined environment isreducing in nature and is produced by an impinging gas-rich flame.

4. The method of claim 1 wherein; said coated article is composed of amaterial that has a coefficient of thermal expansion such that itfractures when rapidly heated to a temperature above its strain point,

said beam of corpuscular energy comprises a laser beam,

and

at least the portion of said coated article that is struck by the laserbeam is preheated to a temperature near its strain point.

5. The method of claim 4 wherein;

said article comprises a glass body, and

said coating comprises a pigmented light-transmitting glaze thatincludes a fused glass frit.

6. The method of claim 5 wherein:

said glass body comprises an envelope for an electric lamp,

said light-transmitting glaze contains a white pigment,

said predetermined environment is reducing in nature, and

the fused glass frit constituent of said glaze contains lead oxide atleast a portion of which is converted by the localized heating action ofsaid impinging laser beam and said reducing environment into lead sothat said indicia or pattern is defined by silvery-black regions in saidglaze.

7. The method of claim 5 wherein:

said glaze is formed by coating the glass body with a powderedpigment-glass frit mixture that is fired in situ by a gas flame, and

the firing of said pigment-glass frit mixture and the preheating of theglass body near its strain point are concurrently effected by a gasflame.

8. The method of claim 7 wherein said gas flame is oxidizing in natureduring the firing and preheating operation and is subsequently madereducing in nature during the laserscanning and decorating operation.

2. The method of claim 1 wherein said predetermined environment is onewhich is reactive in nature.
 3. The method of claim 2 wherein saidpredetermined environment is reducing in nature and is produced by animpinging gas-rich flame.
 4. The method of claim 1 wherein; said coatedarticle is composed of a material that has a coefficient of thermalexpansion such that it fractures when rapidly heated to a temperatureabove its strain point, said beam of corpuscular energy comprises alaser beam, and at least the portion of said coated article that isstruck by the laser beam is preheated to a temperature near its strainpoint.
 5. The method of claim 4 wherein; said article comprises a glassbody, and said coating comprises a pigmented light-transmitting glazethat includes a fused glass frit.
 6. The method of claim 5 wherein: saidglass body comprises an envelope for an electric lamp, saidlight-transmitting glaze contains a white pigment, said predeterminedenvironment is reducing in nature, and the fused glass frit constituentof said glaze contains lead oxide at least a portion of which isconverted by the localized heating action of said impinging laser beamand said reducing environment into lead so that said indicia or patternis defined by silvery-black regions in said glaze.
 7. The method ofclaim 5 wherein: said glaze is formed by coating the glass body with apowdered pigment-glass frit mixture that is fired in situ by a gasflame, and the firing of said pigment-glass frit mixture and thepreheating of the glass body near its strain point are concurrentlyeffected by a gas flame.
 8. The method of claim 7 wherein said gas flameis oxidizing in nature during the firing and preheating operation and issubsequently made reducing in nature during the laser-scanning anddecorating operation.